Peavey JSX crackling..

Stevepage

At rehearsal today I noticed the JSX crackling and popping every so often. To me it sounds like it could be time for new valves in the power section.

I've been thinking of fitting KT77s instead 
, would it be a simple plug in and bias for those valves or will the amp need to be modded to accomodate the KT77s?

Cabicular

I would give the sockets a quick spray with servisol and jiggle the valves around first
(when the amp is off obviously)

DJH83004

It is definitely worth cleaning the valve bases, including the pre-amp valves, as they tend to be more prone than the power valves (should I say the higher gain stages are more sensitive to poor connections). The KT77s will directly replace EL34s but you must check the bias, as you should do anyway.
From memory on the JSX there is an EL34 / 6L6GC selector switch, leave that in the EL34 position.

Stevepage

Just cleaned the sockets with some electrical contact cleaner. Also fitted and biased a quad set of JJ KT77s. Problem seems to have been sorted and the new valves make it sound incredible. 

Stevepage

So the problem seems to not have disappeared like I thought it had. The JSX is now making a "popping" noise which happens every so often when using the amp. 

Am I right in thinking I may have a bad capacitor

ICBM

Stevepage said:

So the problem seems to not have disappeared like I thought it had. The JSX is now making a "popping" noise which happens every so often when using the amp. 

Am I right in thinking I may have a bad capacitor

Possible, but more likely a bad valve. If you've changed the power valves, try replacing each preamp valve in turn with a new one.

Modulus_Amps

Does the popping go away with the gain knobs all at 0, if yes it is probably the first pre amp valve, if no then it is later in the chain
Does the popping go away with the masters all turned down, if no then it is likely the phase inverter valve.

Stevepage

That's the odd thing the preamp valves are all new too

ICBM

Stevepage said:

That's the odd thing the preamp valves are all new too

Was it doing it before you replaced them?

Stevepage

ICBM said:

Stevepage said:

That's the odd thing the preamp valves are all new too

Was it doing it before you replaced them?

yeah thats right

ICBM

Bugger. Time for a trip to the tech.

Stevepage

I thought as much. dropping it off to some one tomorrow night

Stevepage

turns out it was a dodgy connector, a quick krimp and tap test and she's sorted